What should have been an erudite defence of UK foreign policy in Iraq and the wider Muslim world by Jack Straw to the Labour conference faithful descended into a PR debacle when Labour stewards were seen to eject a pensioner by the scruff of his neck for voicing his opinion.

The foreign secretary had been explaining why British troops should stay in Iraq when the 82-year-old lifelong Labour party member heckled him, shouting "nonsense" and "it's a lie".

To the horror of delegates and later of TV viewers, Walter Wolfgang appeared to be grabbed by the collar from his seat and manhandled out of the Brighton venue. When another delegate, Steve Forrest, tried to protect him, he also was ejected and had his credentials removed.

As the ejection was played out on news bulletins, party officials finally realised the damage the images were wreaking, playing straight into the hands of critics who have contended that Labour stifles dissenting views among its members.

When Mr Wolfgang tried to re-enter the Brighton conference venue he found himself stopped by the police under the Prevention of Terrorism Act, and his pass was confiscated. His treatment forced an apology from the Labour party chairman, Ian McCartney, while the health minister, Liam Byrne, told Channel 4 News: "I think the stewards did behave completely inappropriately."

The incident soured a speech in which Mr Straw sought to draw together strands of foreign policy to meet Tony Blair's vision of a faster-changing world.

His strongest words were reserved for bringing Turkey into the EU: "Anchor Turkey in the west and we gain a beacon of democracy and modernity - a country with a Muslim majority - which will be a shining example across the whole of its neighbouring region." He also sent a message to EU foreign ministers who meet on Monday to rule on Turkey's application, telling delegates: "Turkey would lose from a no decision. But Europe and its people would lose even more."

On Iraq, Mr Straw tried to compare the speed of the return of democracy with the rebuilding of Germany after the second world war by saying that it had taken two years to establish elections in Iraq, compared with four in Germany.

He praised Iraqi voters for braving the terrorists and said British troops were there "for one reason only", to help the Iraqi government build "a secure, democratic and stable nation".

Earlier, the T&G union's assistant general secretary, Barry Camfield, had said: "Our troops should be pulled out now and quickly ... I ask you in all conscience: are 100,000 civilian dead a price worth paying? Are the scores of British soldiers dead a price worth paying?"